Method of working pure iron.



urrn sTArrnsra rENT onnio.

ROBERT B. CARNAHAN, JR, 0F MIDDLETOWN, OHIO, ASSIGNOR TO THE INTERNA- TIONAL METAL PRODUCTS 00., 0F MIDDLETOWN, OHIO.

METHOD OF WORKING- PURE IRON.

No Drawing.

have invented certain new and useful Improvements in the Method of Working Pure Iron, of which the following is a specification.

In dealing with pure iron such, for instance, as-is set forth in Carnahans United States Letterslatents No. 940,784, November 23, 1909, No. 940,785, November 23, 1909, and such alloys thereof as set forth in Letters Patent No. 1,035,9l7, August 20th, 1912, and No. 1,035,948 August- 20th, 1912, which'iron is extremely low in carbon and manganese, it has been found that a mass of the iron at high heat may be worked with facility as by rolling or forging, to effect such degree of reduction as is possible before a certain low temperature is reached, it beingthus possible to finish comparativelylarge masses at a single heat. But it has been found that when the mass has had its temperature lowered to a certain extent,

as by rather extended consumption of time in rolling or forging, this pure iron loses much of its useful malleability, and while 'it may stand the desired degree of reduction, the product is seriously defective, and often, fatally so, on account of cracking, checking,

etc. The first thought would be to re-heat the iron before this serious drop in temperature occurs. But I have discovered that with iron of the character referred to this non-malleability of the iron extends through a zone, which 'may be called the zone of critical temperature. When the temperature has fallen below this zone the iron again takes on its useful malleability.

The present invention provides for the extended reduction, by rolling or forging, of this peculiar iron, by doing such work of reduction as can be well done,before the upper limit of the zone of non-malleability is reached, and then arresting the process of reduction until the temperature has fallen Specification of Letters Patent.

Application filed January 16, 1913.

Patented Mar. 10, 1914.

Serial No. 742,400.

below the lower limit of the zone of nonl'ualleability, after which the reduction may be continued and completed. 'It thus be comes possible, in the rolling mill, to produce comparatively small sections from large ingots, without re-heatin and, similarly, in forging, reat reductions in sections may be effected at a single heating.

The upper and lower limits of the zone of non-malleability may be determined by experience gotten from preliminary testing of the iron, the upper limit of temperature being that at which the iron begins to check or crack under the rolls or hammer, and the lower temperature of the zone being that under which checking or cracking ceases to take place, and it Will of course be under stood that in carrying out the present process a reasonably safe margin should be left above the upper limit and below the lower limit of the zone of non-malleability.

It is difficult to ex ress the limits of the zone of non-mallcability of this peculiar iron in degrees of temperature, or in color, but it is suggested that 1000 C. for the upper limit and 800 C. for the lower limit may be taken. As to color it is su gested that there be taken a dark orange or the upper limit and a good cherry red for the lower limit of the zone of non-malleability.

In explaining the principle of my invention to the best of my present ability, I would say that the zone of non-malleability probably corresponds with the transitionary stage when the iron changes its allotropic condition in passing from the amma to the beta or alpha state, such condition of nonmalleability not obtaining if the metal, instead of being the pure iron in question, contains material quantities of carbon or manganese. It will, of course, be understood that the resent invention does not concern itself with the physical characteristics of the metal resulting from the working, but entirely to the integrity of the structure of the metal being worked. In otherwords, my process results in a practically flawless structure of materiahregarde less of the physical properties of that structure of material'after being produced.

I claim The improved method of Working pure iron Which consists in working the metal at temperature above that of the zone of nonmalleahility 0f the metal, arresting the Working until the metal shall have cooled to a point below said zone of non-malleability, 10 and then continuing the Working, substan tially as set forth.

ROBERT B. CAR-NAHAN, JR. \Vitnesses:

M. F. COUGHLIN, P. W. BAUMANN. 

